there may be what look like coffee grounds in your vomit, which means the blood has been in your stomach for a few hours

Keep a small sample of the vomit to show your GP or the doctor treating you. It will give them a much better idea of what's wrong.

What to expect when you see a doctor

Unless you're perfectly well and the cause is obvious to your GP or doctor – for example, swallowing blood from a nosebleed – you should be admitted to hospital straight away for tests.

These will include blood tests and an endoscopy. An endoscopy involves examining the inside of your digestive tract with a thin, flexible tube that has a light and camera at one end.

It's important to confirm that the blood you've vomited has come from your stomach or gullet (oesophagus) and you haven't coughed it up from your airways or lungs, which would indicate a completely different problem.